Dear sir,

I am not able to create a spares matrix by the following code.

```
import numpy as N
import scipy.sparse
source_coord = N.array([0,0,0], dtype=N.float64)
field_pts = N.array([1,0,0])*(N.arange(90)/100+1/10)[:, N.newaxis]
domain_size = N.array([2*3]*3)
import dolfin
B=[[1,2],[3,4]]
A=dolfin.cpp.la.uBLASSparseMatrixMatrix()
print(A)
```